“Don’t drink the coffee on airplanes. It’s the same potable water that goes through the bathroom system,” the unknown flight attendant told the website Vice.com.

The flight attendant further explained that their airline had a test for E.coli in their water and it did not pass.

“And then maintenance came on and hit a couple [of] buttons and it passed,” the flight attendant said.

The anonymous flight attendant advised to avoid any hot water or tea, and to instead ask for bottled water or ice.

Drinking water safety on airlines is regulated by the Environmental Protection Agency (EPA), Food and Drug Administration (FDA), and Federal Aviation Administration (FAA). The EPA monitors systems that supply water to airports and onboard aircraft, while the FDA manages the water used in food and drink preparation and water supply lines for the aircraft. Lastly, the FAA supervises airline operation and maintenance programs, such as the drinking water system. (Related: CounterThoughts: Water on airplanes, drive-through Rx and doctor appointments (satire).)

The anonymous flight attendant is not the first person to make claims regarding the cleanliness of the water in airplanes. In fact, another flight attendant told the Business Insider in 2017 that you should never drink tap water in airplanes because it can be dirty. Moreover, the attendant said that flight attendants do not drink hot water during flights.

The reason for this is that even though the water tanks do get cleaned, flight attendants never know when or how frequently these are done. This has led them to be doubtful about the cleanliness of the water.

“The regulation gives broad discretion to airlines on how often they must test the water and flush the tanks. AFA does not believe this regulation goes far enough or is sufficiently enforced,” the AFA said.